package com.springtest.map;

import org.junit.Test;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * HashMapA
 * HashMap是一个最常用的Map，它根据键的hashCode值存储数据，根据键可以直接获取它的值，具有很快的访问速度。
 * HashMap最多只允许一条记录的键为null，不允许多条记录的值为null。HashMap不支持线程的同步，
 * 即任一时刻可以有多个线程同时写HashMap，可能会导致数据的不一致。如果需要同步，
 * 可以用Collections.synchronizedMap(HashMapA map)方法使HashMap具有同步的能力。
 * Created by Joker on 2017/8/24.
 */
public class HashMapA {

    private Map<String, String> map = new java.util.HashMap<>();

    @Test
    public void test() throws InterruptedException {
        //HashMap多线程,线程不安全,此处使用Collections.synchronizedMap使HashMap具有同步能力
        Collections.synchronizedMap(map);
        ExecutorService executorService = Executors.newCachedThreadPool();
        executorService.submit(() -> map.put(null, null));
        executorService.submit(() -> map.put("1", "A"));
        executorService.submit(() -> map.put("2", "B"));
        Thread.sleep(1000);
        for (Map.Entry<String, String> key : map.entrySet()) {
            System.out.println(String.format("[key]=%s\t[value]=%s", key.getKey(), key.getValue()));
        }
    }


}

package com.springtest.map;

import org.junit.Test;

import java.util.Hashtable;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * HashTableA
 * Hashtable与HashMap类似，不同的是：它不允许记录的键或者值为空；它支持线程的同步，
 * 即任一时刻只有一个线程能写Hashtable，然而，这也导致了Hashtable在写入时会比较慢
 * Created by Joker on 2017/8/24.
 */
public class HashTableA {

    @Test
    public void test() throws InterruptedException {

        //Hashtable本身就是同步机制,所以比较慢
        Map<String, Object> map = new Hashtable<>();
        ExecutorService executorService = Executors.newCachedThreadPool();
        //executorService.execute(() -> map.put(null, null));
        executorService.execute(() -> map.put("1", "A"));
        executorService.execute(() -> map.put("2", "B"));
        Thread.sleep(1000);
        Iterator<Map.Entry<String, Object>> it = map.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry<String, Object> keyValue = it.next();
            System.out.println(String.format("[key]=%s\t[value]=%s", keyValue.getKey(), keyValue.getValue()));
        }

    }

}

package com.springtest.map;

import org.junit.Test;

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * LinkedHashMapA
 * LinkedHashMap保存了记录的插入顺序，在用Iteraor遍历LinkedHashMap时，
 * 先得到的记录肯定是先插入的。在遍历的时候会比HashMap慢。有HashMap的全部特性。
 * Created by Joker on 2017/8/24.
 */
public class LinkedHashMapA {

    @Test
    public void test() throws InterruptedException {

        //多线程,线程不安全
        Map<String, Object> map = new LinkedHashMap<>();
        ExecutorService executorService = Executors.newCachedThreadPool();
        executorService.execute(() -> {
            map.put(null, null);
            map.put("1", "A");
            map.put("2", "B");
            map.put("3", "C");
            map.put("4", "D");
            map.put("5", "E");
        });
        Thread.sleep(1000);
        Iterator<Map.Entry<String, Object>> it = map.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry<String, Object> keyValue = it.next();
            System.out.println(String.format("[key]=%s\t[value]=%s", keyValue.getKey(), keyValue.getValue()));
        }

    }

}

package com.springtest.map;

import org.junit.Test;

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * TreeMapA
 * TreeMap能够把它保存的记录根据键排序，默认是按升序排序，也可以指定排序的比较器。
 * 当用Iteraor遍历TreeMap时，得到的记录是排过序的。TreeMap的键和值都不能为空。
 * TreeMap取出来的是排序后的键值对。但如果您要按自然顺序或自定义顺序遍历键，那么TreeMap会更好。
 * Created by Joker on 2017/8/24.
 */
public class TreeMapA {

    @Test
    public void test() throws InterruptedException {
        //多线程,线程不安全
        Map<String, Object> map = new TreeMap<>();
        ExecutorService executorService = Executors.newCachedThreadPool();
        executorService.execute(() -> {
            //map.put(null, null);
            map.put("4", "D");
            map.put("2", "B");
            map.put("3", "C");
            map.put("5", "E");
            map.put("1", "A");
        });
        Thread.sleep(1000);
        Iterator<Map.Entry<String, Object>> it = map.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry<String, Object> keyValue = it.next();
            System.out.println(String.format("[key]=%s\t[value]=%s", keyValue.getKey(), keyValue.getValue()));
        }
    }

}